ORLANDO, Fla.--(BUSINESS WIRE)--Dec. 7, 2015--
Seattle
Genetics, Inc. (Nasdaq: SGEN) today highlighted data presentations
evaluating ADCETRIS (brentuximab vedotin) in frontline non-Hodgkin
lymphoma at the 57thAmerican Society of Hematology (ASH)
Annual Meeting and Exposition taking place in Orlando, Florida, December
5-8, 2015. The data include an oral presentation highlighting updated
results from an ongoing phase 2 clinical trial evaluating ADCETRIS in
combination with chemotherapy for newly diagnosed, high risk diffuse
large B-cell lymphoma (DLBCL) patients. In addition, a poster
presentation highlights a three-year durability analysis from a phase 1
clinical trial of ADCETRIS in combination with chemotherapy for the
treatment of newly diagnosed peripheral T-cell lymphoma, also known as
mature T-cell lymphoma (MTCL), patients. ADCETRIS is an antibody-drug
conjugate (ADC) directed to CD30, a defining marker of classical Hodgkin
lymphoma and is expressed on several types of non-Hodgkin lymphoma.

“There is a significant need to improve frontline treatment options in
aggressive non-Hodgkin lymphomas. In particular, newly diagnosed
patients with high-intermediate and high-risk DLBCL and MTCL have
estimated three-year progression-free survival rates of approximately 55
percent and 30 percent, respectively,” said Jonathan Drachman, M.D.,
Chief Medical Officer and Executive Vice President, Research and
Development at Seattle Genetics. “ADCETRIS has demonstrated high
complete remission and progression-free survival rates when added to
frontline chemotherapy regimens for DLBCL and MTCL. Our efforts to
redefine frontline therapy for these diseases are part of our goal to
establish ADCETRIS as the foundation of care for all CD30-expressing
lymphomas.”

ADCETRIS is currently not approved for the treatment of frontline DLBCL
and MTCL. For more information about the clinical trials, including
enrolling centers, visit www.clinicaltrials.gov.

Updated interim results were reported from an ongoing phase 2 clinical
trial evaluating ADCETRIS in combination with the standard of care
regimen consisting of rituximab (Rituxan), cyclophosphamide,
doxorubicin, vincristine and prednisone (RCHOP) in frontline
high-intermediate and high-risk DLBCL. Patients were randomized to
receive standard dose RCHOP with either 1.2 milligrams per kilogram
(mg/kg) or 1.8 mg/kg of ADCETRIS. The trial was designed to assess
antitumor activity and the safety profile of ADCETRIS plus RCHOP in
these patients. Exploratory endpoints included CD30 expression measured
by immunohistochemistry (IHC) testing and the relationship between CD30
expression and response.

Data were reported from 51 frontline DLBCL patients with a median age of
67 years. Seventy-one percent of patients in the trial had stage IV
disease, 37 percent were considered high-risk and 63 percent were
considered high-intermediate risk. Key findings presented by Christopher
Yasenchak, M.D., Willamette Valley Cancer Institute and Research
Center/US Oncology Research, include:

Of 25 evaluable patients who had CD30-expressing disease (one percent
expression or greater), 21 patients (84 percent) obtained an objective
response, including 19 patients (76 percent) with a complete remission
and two patients (eight percent) with a partial remission. The
estimated progression-free survival rate for CD30-positive patients at
both 12 and 15 months was 83 percent.

Subsets of patients known to have a poor prognosis appear to have
favorable outcomes:

Eleven patients with CD30-positive activated B-cell like (ABC)
DLBCL had a complete remission rate of 73 percent (eight of 11
patients). The estimated progression-free survival rate for these
patients at both 12 and 15 months was 80 percent.

Six patients with Epstein-Barr virus (EBV)-positive lymphoma had a
complete remission rate of 83 percent (five of six patients). The
estimated progression-free survival rate for these patients at 12
months was 83 percent.

The most common treatment-emergent adverse events of any grade were
fatigue and peripheral sensory neuropathy (63 percent each), diarrhea
and nausea (57 percent each), and neutropenia and vomiting (37 percent
each).The most common Grade 3 or 4 adverse events were febrile
neutropenia (31 percent), neutropenia (33 percent) and anemia (24
percent). Based on an increased rate of Grade 3 peripheral neuropathy
observed in the first 10 patients treated on the 1.8 mg/kg arm,
remaining patients were treated with 1.2 mg/kg of ADCETRIS.

Based on these data, the phase 2 trial has been amended to add a
randomized cohort exploring the activity and safety of ADCETRIS plus
RCHP (without vincristine) versus RCHOP in frontline patients with
CD30-expressing high-intermediate or high-risk DLBCL. Separately, a
randomized phase 2 trial is also ongoing evaluating rituximab and
bendamustine with or without ADCETRIS in relapsed or refractory DLBCL.

Data were reported from 26 frontline MTCL patients who received the
combination regimen of ADCETRIS plus cyclophosphamide, doxorubicin and
prednisone (CHP). Patients who achieved at least a partial remission
with combination therapy were eligible to receive continued single-agent
ADCETRIS treatment. The median age of patients was 56 years. Nineteen
patients (73 percent) had a subtype of MTCL called systemic anaplastic
large cell lymphoma (sALCL), including 16 patients (62 percent) with
anaplastic lymphoma kinase (ALK) negative disease, which is typically
associated with a poor prognosis. Seven patients had a diagnosis of
other types of MTCL. The majority of patients had advanced stage disease
and were considered high risk.

Updated key findings based on a median observation time of 38.7 months
from first dose of therapy include:

The estimated three-year progression-free survival rate was 52
percent, with no patients receiving a consolidative stem cell
transplant in first remission. There have been no progression events
since the previous presentation at the European Society for Medical
Oncology (ESMO) Congress in September 2014. The estimated median
progression-free survival has not yet been reached.

The most common adverse events of any grade occurring in more than 30
percent of patients were nausea and peripheral sensory neuropathy (69
percent each), diarrhea (62 percent), fatigue (58 percent) and hair
loss (54 percent). The most common Grade 3 or higher adverse events
occurring in more than 10 percent of patients were febrile neutropenia
(31 percent), neutropenia (23 percent), anemia (15 percent) and
pulmonary embolism (12 percent).

Seventy-three percent of patients (19 of 26) experienced peripheral
neuropathy, the majority of which was Grade 1 or 2. Ninety-five
percent of these patients had complete resolution or some improvement
of their symptoms at last follow-up with a median time to resolution
of 1.3 months.

A global phase 3 study called ECHELON-2 is currently enrolling patients.
The ECHELON-2 trial is a randomized, double-blind, placebo-controlled,
multi-center trial designed to investigate A+CHP versus CHOP as
frontline therapy in patients with CD30-positive MTCL. Approximately 450
patients (approximately 225 patients per treatment arm) will be
randomized to receive A+CHP or CHOP every three weeks for six to eight
cycles.

About ADCETRIS

ADCETRIS is being evaluated broadly in more than 70 ongoing clinical
trials, including the phase 3 ALCANZA trial and two additional phase 3
studies, ECHELON-1 in frontline classical HL and ECHELON-2 in frontline
mature T-cell lymphomas, as well as trials in many additional types of
CD30-expressing malignancies, including B-cell lymphomas.

ADCETRIS is an ADC comprising an anti-CD30 monoclonal antibody attached
by a protease-cleavable linker to a microtubule disrupting agent,
monomethyl auristatin E (MMAE), utilizing Seattle Genetics’ proprietary
technology. The ADC employs a linker system that is designed to be
stable in the bloodstream but to release MMAE upon internalization into
CD30-expressing tumor cells.

ADCETRIS for intravenous injection has received approval from the FDA
for three indications: (1) regular approval for the treatment of
patients with classical HL after failure of autologous hematopoietic
stem cell transplantation (auto-HSCT) or after failure of at least two
prior multi-agent chemotherapy regimens in patients who are not
auto-HSCT candidates, (2) regular approval for the treatment of
classical HL patients at high risk of relapse or progression as
post-auto-HSCT consolidation, and (3) accelerated approval for the
treatment of patients with systemic anaplastic large cell lymphoma
(sALCL) after failure of at least one prior multi-agent chemotherapy
regimen. The sALCL indication is approved under accelerated approval
based on overall response rate. Continued approval for the sALCL
indication may be contingent upon verification and description of
clinical benefit in confirmatory trials. Health Canada granted ADCETRIS
approval with conditions for relapsed or refractory HL and sALCL.

ADCETRIS was granted conditional marketing authorization by the European
Commission in October 2012 for two indications: (1) for the treatment of
adult patients with relapsed or refractory CD30-positive HL following
autologous stem cell transplant (ASCT), or following at least two prior
therapies when ASCT or multi-agent chemotherapy is not a treatment
option, and (2) the treatment of adult patients with relapsed or
refractory sALCL. ADCETRIS has received marketing authorization by
regulatory authorities in more than 55 countries. See important safety
information below.

Seattle Genetics and Takeda are jointly developing ADCETRIS. Under the
terms of the collaboration agreement, Seattle Genetics has U.S. and
Canadian commercialization rights and Takeda has rights to commercialize
ADCETRIS in the rest of the world. Seattle Genetics and Takeda are
funding joint development costs for ADCETRIS on a 50:50 basis, except in
Japan where Takeda is solely responsible for development costs.

About Seattle Genetics

Seattle Genetics is a biotechnology company focused on the development
and commercialization of innovative antibody-based therapies for the
treatment of cancer. Seattle Genetics is leading the field in developing
antibody-drug conjugates (ADCs), a technology designed to harness the
targeting ability of antibodies to deliver cell-killing agents directly
to cancer cells. The company’s lead product, ADCETRIS®
(brentuximab vedotin) is a CD30-targeted ADC that, in collaboration with
Takeda Pharmaceutical Company Limited, is commercially available in more
than 55 countries, including the U.S., Canada, Japan and members of the
European Union. Additionally, ADCETRIS is being evaluated broadly in
more than 70 ongoing clinical trials in CD30-expressing malignancies.
Seattle Genetics is also advancing a robust pipeline of clinical-stage
programs, including vadastuximab talirine (SGN-CD33A; 33A), denintuzumab
mafodotin (SGN-CD19A; 19A), SGN-LIV1A, SGN-CD70A, ASG-22ME, ASG-15ME and
SEA-CD40. Seattle Genetics has collaborations for its ADC technology
with a number of leading biotechnology and pharmaceutical companies,
including AbbVie, Agensys (an affiliate of Astellas), Bayer, Genentech,
GlaxoSmithKline and Pfizer. More information can be found at www.seattlegenetics.com.

Serious infections and opportunistic infections: Infections
such as pneumonia, bacteremia, and sepsis or septic shock (including
fatal outcomes) have been reported in patients treated with ADCETRIS.
Closely monitor patients during treatment for the emergence of
possible bacterial, fungal or viral infections.

Increased toxicity in the presence of severe renal impairment: The
frequency of ≥Grade 3 adverse reactions and deaths was greater in
patients with severe renal impairment compared to patients with normal
renal function. Avoid the use of ADCETRIS in patients with severe
renal impairment.

Increased toxicity in the presence of moderate or severe hepatic
impairment: The frequency of ≥Grade 3 adverse reactions and deaths
was greater in patients with moderate or severe hepatic impairment
compared to patients with normal hepatic function. Avoid the use of
ADCETRIS in patients with moderate or severe hepatic impairment.

Hepatotoxicity: Serious cases of hepatotoxicity, including
fatal outcomes, have occurred with ADCETRIS. Cases were consistent
with hepatocellular injury, including elevations of transaminases
and/or bilirubin, and occurred after the first dose of ADCETRIS or
rechallenge. Preexisting liver disease, elevated baseline liver
enzymes, and concomitant medications may also increase the risk.
Monitor liver enzymes and bilirubin. Patients experiencing new,
worsening, or recurrent hepatotoxicity may require a delay, change in
dose, or discontinuation of ADCETRIS.

Progressive multifocal leukoencephalopathy (PML): JC virus
infection resulting in PML and death has been reported in
ADCETRIS-treated patients. First onset of symptoms occurred at various
times from initiation of ADCETRIS therapy, with some cases occurring
within 3 months of initial exposure. In addition to ADCETRIS therapy,
other possible contributory factors include prior therapies and
underlying disease that may cause immunosuppression. Consider the
diagnosis of PML in any patient presenting with new-onset signs and
symptoms of central nervous system abnormalities. Hold ADCETRIS if PML
is suspected and discontinue ADCETRIS if PML is confirmed.

Pulmonary Toxicity: Events of noninfectious pulmonary toxicity
including pneumonitis, interstitial lung disease, and acute
respiratory distress syndrome, some with fatal outcomes, have been
reported. Monitor patients for signs and symptoms of pulmonary
toxicity, including cough and dyspnea. In the event of new or
worsening pulmonary symptoms, hold ADCETRIS dosing during evaluation
and until symptomatic improvement.

Certain of the statements made in this press release are forward
looking, such as those, among others, relating to our future clinical
trials, potential future uses of ADCETRIS and our goal to establish
ADCETRIS as the foundation of therapy for a broad array of
CD30-expressing lymphomas. Actual results or developments may differ
materially from those projected or implied in these forward-looking
statements. Factors that may cause such a difference include the risks
of adverse events associated with ADCETRIS use, negative or unexpected
ADCETRIS clinical trial results even after promising results in earlier
company and investigator-sponsored trials, and adverse regulatory
actions affecting ADCETRIS. More information about the risks and
uncertainties faced by Seattle Genetics is contained under the caption
“Risk Factors” included in the company’s Quarterly Report on Form 10-Q
for the quarter ended September 30, 2015 filed with the Securities and
Exchange Commission. Seattle Genetics disclaims any intention or
obligation to update or revise any forward-looking statements, whether
as a result of new information, future events or otherwise.